DQ3-1 “Data flow diagrams and flowcharts provide redundant pictures of an information system. We don’t need both.” Discuss.
DQ3-2 “It is easier to learn to prepare data flow diagrams, which use only a few symbols, than it is to learn to prepare flowcharts, which use a number of different symbols.” Discuss.
DQ3-3 Describe the who, what, where, and how of the following scenario: A customer gives his pur- chase to a sales clerk, who enters the sale in a cash register and puts the money in the
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register drawer. At the end of the day, the sales clerk gives the cash and the register tape to the cashier.
DQ3-4 Why are there many correct logical DFD solutions? Why is there only one correct physical DFD solution?
DQ3-5 Explain why a flow from a higher- to a lower-numbered bubble on a logical DFD is a phys- ical manifestation of the system. Give an example.
DQ3-6 Compare and contrast the purpose of and techniques used in drawing physical DFDs and logical DFDs.
DQ3-7 “If we document a system with a systems flowchart, data flow diagrams, and E-R dia- grams, we have overdocumented the system.” Discuss.
DQ3-8 “Preparing a table of entities and activities as the first step in documenting systems seems to be unnecessary and unduly cumbersome. It would be a lot easier to bypass this step and get right to the necessary business of actually drawing the diagrams.” Do you agree? Discuss fully.
DQ3-9 “In terms of the sequence used in documenting systems, it would be easier to prepare a systems flowchart before we prepare a data flow diagram.” Do you agree? Discuss fully.
DQ3-10 “Since there are computer-based documentation products that can draw data flow dia- grams and systems flowcharts, learning to draw them manually is a waste of time.” Do you agree? Discuss fully.
PROBLEMS
P3-1 Prepare a narrative to describe the system depicted in the physical DFD in Figure 3.14.
Figure 3.14 Physical DFD for Problem 3-1
1.0 Sales Office Customer telephone order 3.0 Warehouse 2.0 Computer 4.0 Shipping Carrier Annotated picking ticket (copy 1) Order data Picking ticket (2-part) Order acceptance Packing slip (copy 1) Annotated picking
ticket (copy 2)—paper
Inventory master data—disk Telephone
acknowledgement Customer
Packing slip (copy 2), Annotated picking ticket (copy 1)—paper
Customer master data—disk
Accounts receivable master data—disk
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P3-2 Prepare a narrative to describe the system depicted in the logical DFD in Figure 3.15.
P3-3 Prepare a narrative to describe the system depicted in the flowchart in Figure 3.16.
P3-4 a. List the entities and activities in Figure 3.17 (p. 99).
b. Prepare a statement for each entity-relationship pair in Figure 3.17. (There are six pairs.) Each statement should explain the relationship category (e.g., “N to 1,” “1 to N,” “1 to 1,” etc.). For example, to describe the order-customer relationship in Figure 3.8 (p. 78), we might say: “Orders are received from customers. A customer may place many orders (N) but each order is from only one customer (1), an N to 1 relationship.”
P3-5 through P3-8 Problems 5 through 8 are based on the following two narratives. Lincoln Company de- scribes sales and credit card billing systems. Bono Insurance describes an automobile in- surance order entry and billing system. For those who wish to test their documentation skills beyond these problems, there are narratives at the end of Chapters 10 through 12 and on the CD accompanying this text. Note that for the Lincoln case we do not discuss, and you should ignore, the handling of cash received at the time of a sale.
Lincoln Company
Lincoln Company operates pet supply stores at many locations throughout New England. The company’s headquarters are in Boston. The company accepts cash and its own Lincoln charge card (LCC). LCC billing and the treasury functions are located at headquarters.
At each store a customer presents the item(s) to be purchased along with cash or a LCC. Sales clerks prepare LCC slips and then all sales, cash and charge, are keyed into the cash register. At the end of the shift, the clerk forwards the LCC slips to the store cashier (again, as noted above, ignore the handling of the cash). The store cashier batches the LCC slips and sends the batches to the cash receipts section in Boston at 5:00 P.M. each day.
As each sale is keyed by the sales clerks, Lincoln’s central computer system captures the sales data and stores them on a disk (“sales events data”). Each night, the computer prints a sales report summarizing each store’s sales events data. On the following morn- ing, the sales report is sent to the cash receipts section, where the LCC slips for each store are reconciled to the line on the sales report that totals LCC sales for that store. The LCC slips are then sent to Lincoln’s IT division, where data preparation clerks scan the LCC slips to record the charges on a disk (“credit sales data”). At 9:00 each evening the disk containing the Credit sales data is sent to the computer room, where it is used to update the accounts receivable master data (also on disk). Each month, the computer prepares
Figure 3.15 Logical DFD for Problem 3-2
Customer Contract file 1.0 Prepare and record contract Operations office Sales office Monthly statement Service request Hours worked report Accounts receivable master data Hours worked file Contract (copy) 3.0 Prepare monthly statements Contracts not billed report 2.0 Record hours worked
P
ar
t 1
AIS Foundations
Figure 3.16 Flowchart for Problem 3-3
Customer Customer order Log order Daily event log Error routine not shown Accepted order Review order, check credit, log order Inventory master data Clerk's log Record shipment Daily event log Filled order Warehouse A
CENTRAL SALES OFFICE COMPUTER WAREHOUSE SUPERVISOR
Filled orders Key order
Compare
Check inventory, record order, print
packing slip Printed at regional warehouse System log Accounts receivable master data Sales order master data Print daily event log (at the end of each day)
A Sales journal Warehouse Filled order Accepted input Enter order number and quantities shipped
CORPORATE OFFICE REGIONAL WAREHOUSE
N
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Figure 3.17 Entity-Relationship (E-R) Diagram for Problem 3-4
ORDER CUSTOMER INVENTORY SHIPMENT made by order item madeto ship item fills M N M N N N 1 1 SALESPERSON taken by 1 N 1 N
customer statements that summarize the LCC charges, and sends the statements to the customers.
Bono Insurance
Bono Insurance Company of Needham, Massachusetts, processes its automobile insurance policies on a batch-oriented computer system with magnetic disk storage. Customers send requests for auto insurance into the Needham sales office where sales clerks prepare policy request forms. These documents are forwarded to the input preparation section where data entry clerks use net- worked PCs to key and key-verify the data contained on the doc- uments to a disk (“policy events”).
Each evening, computer operations retrieves the policy events data from the network and edits the data on the computer and then sorts the data in policy number sequence. Events data that do
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not pass the edits are deleted from the events data disk and printed on an error report. The error report is sent to the sales office where sales clerks review the report, correct the errors (contacting the customer, if necessary), and prepare another policy request form. These forms are submitted to data preparation each day along with other policy request forms.
In addition to the error report, the computer also prints a summary report listing the good events data. This report is sent to the sales office where the sales clerks compare the report to the copy of the policy request form that they previously filed. If everything checks out, they notify computer operations to go ahead with processing. When notified, computer operations processes the correct events data against the policyholder master data to create a new policy record. Each evening, a disk, which was created during the pro- cessing run, is used to print premium notices that are sent to the customer.
P3-5 a. Prepare a table of entities and activities based on either the Lincoln Company or the Bono Insurance narrative.
b. Construct a context diagram based on the table you prepared in part a.
P3-6 Prepare a physical DFD based on the output from Problem 5.
P3-7 a. Prepare an annotated table of entities and activities based on the output from Problems 5 and 6. Indicate on this table the groupings, bubble numbers, and bubble titles to be used in preparing a level 0 logical DFD.
b. Prepare a logical DFD (level 0 only) based on the table you prepared in part a.
P3-8 Construct a systems flowchart based on the narrative and the output from Problems 5 through 7.
P3-9 A description of fourteen typical information processing routines is given here, along with ten numbered excerpts from systems flowcharts (see Figure 3.18).
Match the flowcharting segments with the descriptions to which they correspond. Four descriptions will be left blank.
a. Data on source documents are keyed to an off-line disk. b. A deposit slip and check are sent to a bank.
c. A printed output document is filed.
d. Output is provided to a display device at a remote location.
e. A clerk manually posts sales invoices to the accounts receivable ledger. f. A report is printed from the contents of a disk.
g. Data stored on a disk is sorted and placed on another disk. h. Data on a magnetic tape are printed during an off-line operation. i. Data are keyed from a terminal at a remote location.
j. A batch total is compared to the total reflected on an error and summary report. k. Magnetic tape input is used to update master data kept on a disk.
l. The cash receipts summary report is sent by the accounts receivable department to the general ledger bookkeeper.
m. Input stored on two magnetic disks is merged.
n. Programmed edits are performed on key input, the data entry clerk investigates excep- tions and keys in corrections, then data on the disk are updated.
P3-10 Refer to Figure 3.12 (p. 88), the level 0 DFD of Causeway’s cash receipts system.
a. Construct a diagram 1, which “explodes” process 1.0, “Capture cash receipts,” down to the next level.
b. Construct a diagram 2, which “explodes” process 2.0, “Record customer collections,” down to the next level.
c. Construct a diagram 3, which “explodes” process 3.0, “Prepare deposit,” down to the next level.
d. Construct a diagram 4, which “explodes” process 4.0, “Prepare cash receipts total,” down to the next level.
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Figure 3.18 Flowchart Segments for Problem 3-9
1 2 3 4
5 6 7
8 9